Simplifying ratios

In this figure, it is easy to see that the ratio of yellows to greens is $\frac{6}{8}$. If we put circles around each column of tiles

we can see that the ratio of yellow columns to green columns is $\frac{3}{4}$.

Since the number of tiles never changed - only how we looked at them - this shows that the ratios $\frac{6}{8}$ and $\frac{3}{4}$ are equivalent to each other. In other words, $$\frac{6}{8}\,=\,\frac{3}{4}$$